import sys

def fib(n):
    if n > 1:
        return n * fib(n-1)
    else:
        return 1

if __name__ == '__main__':
    if len(sys.argv) < 2:
        print 'usage %s n' % (sys.argv[0],)
        sys.exit()

    n = int(sys.argv[1])
    print 'fib(%d) = %d' %(n, fib(n))
